Rolling Your Own Config as Code for Anonymous Configs

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Managing configuration as code is a powerful practice
But what happens when the API or SDK you rely on doesn’t support easy comparison of remote and local configurations?

Managing feature flags (or similar settings) through a UI
Managing them via configuration files or APIs—treating configurations as structured, version-controlled code—the approach
All configuration (including feature flags) is defined in code (YAML, JSON, etc.) or via APIs, not manually in a UI
Configurations are stored in version control systems, allowing for change tracking, reviews, and rollbacks
Feature flags can be managed as code by:
- Defining their states and rules in configuration files.
- Using APIs to read, update, and deploy flag configurations, bypassing the need for a UI.
- Integrating with CI/CD pipelines for automated rollout and rollback

Common challenges

No Built-in diff support: Many APIs/SDKs for feature flags or configuration management lack native tools to compare remote and local states
No unique identifiers: Config entries may not have stable names or IDs, making direct comparison tricky
Manual effort: Without automation, tracking changes is error-prone and time-consuming

Specific problem

Setting up configuration as code for ~700 experiments previously stored on the backend for a UI
API/SDK for basic CRUD operations
Getting configurations from remote works
Main issue: No logic to compare remote config (or parts of it) to current local config
Only identifier for configuration is the internal database ID
Doesn’t make sense to store that in the configuration files for multiple reasons
Need a way to compare and know exactly what to change and on which remote entry id

Overview

You can implement a custom logic that:
- Fetches remote configuration via API
- Reads local configuration from your repository
- Normalizes both configurations (e.g., sorts keys, strips metadata)
- Generates signatures or hashes for each config object
- Compares these signatures to detect additions, deletions, or modifications

Fetch and normalize configurations

Remote: Use the API to retrieve the current configuration state
Local: Parse the configuration files from your code repository
Normalize: Sort keys, remove timestamps or irrelevant fields, and ensure consistent formatting

Generate Signatures or Hashes

For each config object, create a hash (e.g., SHA256) of its normalized representation
This allows you to compare objects even without unique names
Use Stable Serialization: Always serialize config objects in a consistent way before hashing
Ignore Non-Essential Fields: Exclude fields like timestamps or autogenerated IDs to avoid false positives

Compare and detect changes

Added: Hashes present locally but not remotely
Removed: Hashes present remotely but not locally
Modified: Hashes with matching structure but differing content

Report or act

Output a report of differences for review
Optionally, automate syncing or alerting based on the detected changes

We’re given a dummy SDK sdk with a few functions out of the box
A response object can be queried for platforms, features, rollouts
Here’s an overview of relevant SDK functionality (given by SDK)
High level functions:
- createConfig(platform, environment, name): creates a config on the given platform
- retrieveConfig(platform, environment, name): gets a config from the given platform
Config level functions:
- getPlatforms()
- getName()
- getRolloutById()
- getFeatures()
- getFeatureById()
- getFeatureByName()
- getFeatureByValue)
- addFeature()
- addRollout()
- changeFeatureName()
- changeFeatureValue()
- clearFeatures()
- commitChanges()
- disableConfig()
- enableConfig()
- removeRollout()
- replaceRollout()

Simple configuration structure for the purpose of this post
Mobile feature flag and rollout management configuration
Enables control over which features are available to users, how widely they are rolled out, and to manage different values and rollout strategies per platform in the production environment
Local configuration as YAML file

name: dummy
kind: mobile
platforms:
  - name: android
    features:
      - name: feature1
        value: 100
      - name: feature2
        value: 0
      - name: feature3
        value: 0
      - name: feature4
        value: 50
    environment:
      - name: production
        enabled: true
    rollout:
      - weight: 33000
        enabled: true
        feature: feature1
      - weight: 33000
        enabled: true
        feature: feature2
      - weight: 34000
        enabled: true
        feature: feature3
      - weight: 0
        enabled: false
        feature: feature4
  - name: ios
    features:
      - name: feature1
        value: 0
      - name: feature2
        value: 10
      - name: feature3
        value: 0
      - name: feature4
        value: 40
    environment:
      - name: production
        enabled: true
    rollout:
      - weight: 33000
        enabled: true
        feature: feature1
      - weight: 33000
        enabled: true
        feature: feature2
      - weight: 34000
        enabled: true
        feature: feature3
      - weight: 0
        enabled: false
        feature: feature4

Remote configuration JSON:

{
  "id": "1",
  "name": "dummy_android",
  "kind": "mobile",
  "created_at": "2025-07-09T12:42:00.953753Z",
  "updated_at": "2025-07-09T12:42:00.953769Z",
  "platforms": [
    {
        "id": "1",
        "name": "android",
        "created_at": "2025-07-09T12:42:00.953681Z",
        "updated_at": "2025-07-09T12:42:00.953698Z",
        "environment": {
            "name": "production",
            "enabled": true
        },
        "features": [
        {
          "id": "1",
          "created_at": "2025-07-09T12:42:00.953547Z",
          "updated_at": "2025-07-09T12:42:00.953627Z",
          "rollout": [
            {
                "id": "1",
                "featureId": "1",
                "created_at": "2025-07-09T12:42:00.953638Z",
                "updated_at": "2025-07-09T12:42:00.953642Z",
                "weight": 33000,
                "enabled": true
            }
            },
            {
                "id": "2",
                "featureId": "2",
                "created_at": "2025-07-09T12:42:00.953638Z",
                "updated_at": "2025-07-09T12:42:00.953642Z",
                "weight": 33000,
                "enabled": true
            },
            {
                "id": "3",
                "featureId": "3",
                "created_at": "2025-07-09T12:42:00.953646Z",
                "updated_at": "2025-07-09T12:42:00.953649Z",
                "weight": 34000,

            },
            {
                "id": "4",
                "featureId": "4",
                "created_at": "2025-07-09T12:42:00.953653Z",
                "updated_at": "2025-07-09T12:42:00.953655Z",
                "weight": 0,
                "enabled": false
            }
        ]
    },
    {
      "id": "platform_ios",
      "name": "ios",
      "created_at": "2025-07-09T12:42:00.953730Z",
      "updated_at": "2025-07-09T12:42:00.953733Z",
      "environment": {
        "name": "production",
        "enabled": true
      },
      "features": [
        {
          "id": "feature_feature1",
          "name": "feature1",
          "value": 0,
          "created_at": "2025-07-09T12:42:00.953703Z",
          "updated_at": "2025-07-09T12:42:00.953706Z",
          "rollout": {
            "weight": 33000,
            "enabled": true
          }
        },
        {
          "id": "feature_feature2",
          "name": "feature2",
          "value": 10,
          "created_at": "2025-07-09T12:42:00.953710Z",
          "updated_at": "2025-07-09T12:42:00.953713Z",
          "rollout": {
            "weight": 33000,
            "enabled": true
          }
        },
        {
          "id": "feature_feature3",
          "name": "feature3",
          "value": 0,
          "created_at": "2025-07-09T12:42:00.953717Z",
          "updated_at": "2025-07-09T12:42:00.953720Z",
          "rollout": {
            "weight": 34000,
            "enabled": true
          }
        },
        {
          "id": "feature_feature4",
          "name": "feature4",
          "value": 40,
          "created_at": "2025-07-09T12:42:00.953723Z",
          "updated_at": "2025-07-09T12:42:00.953726Z",
          "rollout": {
            "weight": 0,
            "enabled": false
          }
        }
      ]
    }
  ]
}

~ stay curious ~